Image sensor, multi-chip module type image sensor and contact image sensor

ABSTRACT

The invention is to suppress a loss in image quality resulting from a sensitivity difference among different colors and to suppress an increase in a chip area. The invention provides for example an image sensor including three light detecting element rows respectively having R, G and B color filters on light detecting apertures, in which the light detecting element in the G light detecting element row has a light detecting area larger than that of the light detecting element in other B and R light detecting element rows and centers of gravity of light detecting parts of the light detecting elements in the respective light detecting element rows are arranged with a constant pitch (pitch Q) among the light detecting element rows and in which the G light detecting element row with a larger light detecting area in the light detecting element is not positioned as an end row among the R, G and B light detecting element rows but as a central light detecting element row.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectric conversion device, andmore particularly to an image sensor having a photoelectric conversionelement and a color filter provided in a light detecting part thereof,on a substrate.

The present invention further relates to a multi-chip module type imagesensor, a contact image sensor and an image reading apparatus, formed byarranging such image sensor by plural units in an array.

2. Related Background Art

As a line-type image reading device in the field of informationprocessing system, instead of the prior reduction-type line sensorutilizing an optical system, developments are being made for anequal-size contact image sensor formed by mounting multiplesemiconductor photosensors.

Also a color sensor is being recently desired instead of the priormonochromatic sensor.

For example, Japanese Patent Application Laid-open No. H03-289856discloses a structure of such sensor. FIGS. 14 to 16 are equivalentcircuit diagrams of an image sensor described in the above-mentionedpatent reference. More specifically, FIG. 14 is a schematic view of asemiconductor image sensor of multi chip module type; FIG. 15 is amagnified view of a part A of the multi-chip module type semiconductorimage sensor; and FIG. 16 is a view showing a configuration of anoptical system utilizing the multi-chip module type semiconductor imagesensor.

In FIGS. 14 and 16, there are shown an original 1, a circuit board 2having desired circuits for mounting semiconductor image sensor,semiconductor image sensors S1 to Sn arranged in a linear array, aCelfoc lens array (trade name of Nippon Plate Glass Co.), and anoriginal illuminating LED array 4. Also a combination of an LED and alight conducting member is often employed instead of the originalilluminating LED array 4.

In FIG. 15, 5 indicates a light detecting aperture on the semiconductorimage sensor. In case of a color sensor, the light detecting aperture 5on the semiconductor image sensor is provided in three rows, which arerespectively provided with red, green and blue color filters as shown inFIG. 15. The light detecting apertures of red, blue and green in a samecolumn have respective outputs to constitute a color light detectingelement. In order to facilitate formation of a color signal from thered, blue and green signals in a subsequent image processing, a pitch Qof the rows (a distance between centers of gravity of the lightdetecting apertures in a sub scanning direction) is selected same as oran integral multiple of a pitch P of the light detecting apertures inthe main scanning direction. FIG. 15 shows a case where the row pitch Qis twice of the pitch P of the light detecting apertures in the mainscanning direction (Q=2P).

A peripheral circuit block 6 is provided on the semiconductor imagesensor for controlling and outputting a photosignal, generated from thelight received by the light detecting aperture.

Such semiconductor image sensor of multi chip module type has a featurecapable of dispensing with a reduction optical system thereby enablingcompactification, and is widely employed in an image processingapparatus such as a facsimile apparatus or a scanner.

However, in case the light detecting apertures in different rows havinga same area as shown in FIG. 15, since the sensitivity is different forthe respective colors depending on the light emission characteristics ofLED, the spectral characteristics of the color filters and the spectralcharacteristics of the light detecting element, the image quality isdetermined by an output of a row corresponding to a color of lowestsensitivity.

In order to avoid such drawback, Japanese Patent Application Laid-openNo. H11-150627 discloses changing the light detecting area of the pixelaccording to the transmittance of the color filter.

However the present inventor has found another drawback, in case ofchanging the light detecting area of the pixel, depending on the row ofpixels (light detecting element row) in which the light detecting areais changed.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image sensor, amulti-chip module type image sensor and a contact sensor, in which anarea of a light detecting aperture is regulated (increased or decreased)according to a sensitivity in order to solve or alleviate theaforementioned drawback, and which can also solve another drawbackresulting from a regulation in the area of the light detecting aperture.

The present invention provides an image sensor including at least threelight detecting element rows each having plural light detecting elementsand a color filter provided on each light detecting element, in whichthe light detecting element in one light detecting element row has alight detecting area larger than that of the light detecting element inthe other light detecting element rows, and the light detecting elementrows are arranged such that gravities of light detecting parts of thelight detecting elements of the respective light detecting element rowsare arranged at a constant pitch:

wherein the light detecting element row with a larger light detectingarea in the light detecting element is positioned between theaforementioned other light detecting element rows.

The present invention also provides an image sensor including at leastthree light detecting element rows each having plural light detectingelements and a color filter provided on each light detecting element, inwhich the light detecting element of at least one light detectingelement row has a light detecting area larger than that of the lightdetecting element in the other at least two light detecting elementrows, and the light detecting element rows are arranged such thatcenters of gravity of light detecting parts of the light detectingelements of the respective light detecting element rows are arranged ata,constant pitch:

wherein the at least one light detecting element row with a larger lightdetecting area of the light detecting element is positioned between theaforementioned other light detecting element rows with a smaller lightdetecting area of the light detecting elements.

The foregoing expression “the at least one light detecting element rowwith a larger light detecting area in the light detecting element ispositioned between the aforementioned other light detecting elementrows” has a following meaning. For the light detecting element rows inwhich the light detecting elements thereof have light detecting areasS1, S2 and S3, in case of S1>S2≧S3, the foregoing expression means thatthe light detecting element row in which the light detecting elementsthereof have a light detecting area S1 is not positioned in the rows onboth ends. Also for the light detecting element rows in which the lightdetecting elements thereof have light detecting areas S1, S2, S3 and S4,in case of S1≧S2>S3≧S4, the foregoing expression means that the lightdetecting element row in which the light detecting elements thereof havea light detecting area S1 or S2 is not positioned in the rows on bothends.

The present invention also provides an image sensor including at leastthree light detecting element rows each having plural light detectingelements and a color filter provided on each light detecting element,and a peripheral circuit unit for controlling and outputting a photosignal generated by the light detecting elements of the at least threelight detecting element rows, in which the light detecting element ofone light detecting element row among the at least three light detectingelement rows has a light detecting area smaller than that in the lightdetecting element of other light detecting element rows, and the lightdetecting element rows are arranged such that centers of gravity oflight detecting parts of the light detecting elements of the respectivelight detecting element rows are arranged at a constant pitch:

wherein the light detecting element row with a smaller light detectingarea in the light detecting element is positioned, among the at leastthree light detecting element rows, in an end row at the side of theperipheral circuit unit.

The present invention also provides an image sensor including plurallight detecting element rows each having plural light detecting elementsand a color filter provided on each light detecting element, in whichcenters of gravity of light detecting parts of the light detectingelements of the respective light detecting element rows are arranged ata constant pitch among the light detecting element rows:

wherein a driving circuit part for reading an electrical signal fromeach light detecting element is provided for each light detectingelement; and

wherein a pitch L of the light detecting elements along a direction ofarray thereof in the plural light detecting element rows, a pitch nL (nbeing a positive integer) of the plural light detecting element rowsalong a direction of arrangement thereof, a width k of the drivingcircuit part in the direction of arrangement of the plural lightdetecting element rows, a width a of a first light detecting aperturewith a largest area among the plural light detecting element rows alongthe direction of arrangement of the plural light detecting element rows,and a width b of a second light detecting aperture with a second largestarea among the plural light detecting element rows along the directionof arrangement of the plural light detecting element rows are selectedthat the width a meets a following relation:(a/2)+k+(b/2)=nL

The expression “width a meets a following relation” includes also asituation where the width a is close to the relation (a/2)+k+(b/2)=nL.More specifically, the width a may be selected smaller than a valuedefined by the aforementioned relation, in consideration for example ofa fluctuation in the manufacture, and such situation is also consideredin the present invention that “the width a is selected to meet therelation”.

The present invention allows to suppress a loss in the image qualityresulting from a sensitivity difference among the colors and to suppressan increase in the chip area.

Also the present invention allows to suppress a photocarrier generationby the light of an unnecessary wavelength region, thereby suppressing acolor mixing and providing a color image of a high quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a first embodiment of a photoelectricconverting device of the present invention;

FIG. 2 is a schematic plan view of a second embodiment of thephotoelectric converting device of the present invention;

FIG. 3 is a schematic cross-sectional view of the second embodiment ofthe photoelectric converting device of the present invention;

FIG. 4 is a schematic cross-sectional view of another second embodimentof the photoelectric converting device of the present invention;

FIG. 5 is a schematic plan view of a third embodiment of thephotoelectric converting device of the present invention;

FIG. 6 is a spectral characteristic chart of an LED for explaining afourth embodiment of the photoelectric converting device of the presentinvention;

FIG. 7 is a spectral characteristic chart of a light detecting elementfor explaining the fourth embodiment of the photoelectric convertingdevice of the present invention;

FIG. 8 is a spectral characteristic chart showing an output of asemiconductor image sensor for explaining the fourth embodiment of thephotoelectric converting device of the present invention;

FIG. 9 is a schematic plan view of a fifth embodiment of thephotoelectric converting device of the present invention;

FIG. 10 is a schematic plan view of a semiconductor image sensor in acomparative example;

FIG. 11 is a schematic plan view of a semiconductor image sensor inanother comparative example;

FIG. 12 is a schematic view of an original image reading apparatus forreading an original image;

FIG. 13 is a block diagram showing a detailed electrical structure of acontrol circuit 210 in FIG. 12;

FIG. 14 is a schematic plan view of a multi-chip module type sensor in aprior technology;

FIG. 15 is a magnified view of a part A in FIG. 14; and

FIG. 16 is a view showing an optical system utilizing the multi-chipmodule type image sensor shown in FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be explainedin detail with reference to the accompanying drawings.

First Embodiment

A configuration of the present invention will be explained while makingcomparison with a prior example.

In case of increasing the area of the light detecting aperture in thelight detecting element row, since a pitch P in the main scanningdirection is determined by specifications of the image sensor, the areais spread in the sub scanning direction thereby improving thesensitivity. FIG. 10 shows a comparative example in which the area isspread in a light detecting aperture 5 (blue) present in the vicinity ofa peripheral circuit block, in comparison with a part of FIG. 15. With arow pitch Q selected equal to or as an integral multiple of the pitch Pof the light detecting apertures in the main scanning direction, theposition of the peripheral circuit block 6 has to be rearrangedcorresponding to the spreading of area. As a result, the semiconductorimage sensor becomes larger in the chip area, thereby resulting in anincrease in the chip cost.

FIG. 11 shows a comparative example, in which a row with a widened areais positioned close to a chip end of the semiconductor image sensor, incomparison with a part of FIG. 15. As shown in FIG. 11, a row pitch Q isselected equal to or as an integral multiple of the pitch P of the lightdetecting apertures in the main scanning direction, as in the case ofFIG. 10. In such case, the chip end position has to be changedcorresponding to the spreading of area. As a result, the semiconductorimage sensor becomes larger in the chip area, thereby resulting in anincrease in the chip cost.

FIG. 1 is a schematic plan view showing a configuration of a firstembodiment of the present invention, and is a magnified view of aboundary portion between two adjacent semiconductor image sensors. Thestructure of a multi-chip module type semiconductor image sensor willnot be explained further, as it is already explained with reference toFIGS. 14 to 16. FIG. 1 shows a case where the row pitch Q is selectedtwice of the pitch P of the light detecting apertures in the mainscanning direction (Q=2P).

In the present embodiment, a row with a widened area is positioned atthe center of three rows, as shown in FIG. 1. Such configuration allowsto retain the advantage of selecting the row pitch Q equal to or as anintegral multiple of the pitch P of the light detecting apertures in themain scanning direction thereby facilitating formation of the colorsignal, and also to resolve or alleviate the drawback of image qualityloss resulting from a sensitivity difference between the colors.

In case of selecting the row pitch Q (distance of centers of gravity ofthe light detecting apertures in the sub scanning direction) equal tothe pitch P of the light detecting apertures in the main scanningdirection, because of the restriction in the row pitch Q (Q=P), the areaspreading of the light detecting aperture in the pixels of the centerrow is limited. However, the row pitch can be made larger by selecting,as in the present embodiment, each row pitch Q as an integral multipleof the pitch P of the light detecting apertures in the main scanningdirection (Q=2P, 3P, . . . ). As a result, the length of the lightdetecting aperture may be made arbitrarily longer in the sub scanningdirection, thereby increasing the area.

As already explained, the area of the light detecting apertures isdetermined according to the light emission characteristics of the lightsource, the spectral characteristics of the color filter and thespectral characteristics of the light detecting element. In the presentembodiment, the area of the light detecting aperture is made larger inthe green row, which is positioned at the center. However, in case alight detecting element row showing a lower sensitivity at a same areaof the light detecting aperture is a red or blue row, the area of thelight detecting aperture may be made larger in such red or blue row,which may be positioned at the center.

Second Embodiment

In the following, the configuration of the present embodiment will beexplained.

The present embodiment shows a case where the areas of the lightdetecting apertures are made all different among the three lightdetecting element rows, in which the light detecting aperture with asmallest area is made smaller than in the case shown in FIG. 15. Also inthe present embodiment, a row having the light detecting aperture of alargest area is positioned at the center, as in the first embodiment.

FIG. 2 shows the configuration of the present embodiment, in which thelight detecting aperture of the smallest area is positioned at a chipend of the semiconductor image sensor. FIG. 3 is a schematiccross-sectional view of the semiconductor image sensor shown in FIG. 2,wherein shown are a semiconductor substrate 7, a light detecting element8 such as a photodiode, a semiconductor device area 9 for forming aperipheral circuit block 6, and a light shielding layer 10 formed on aninterlayer film 11. A light detecting aperture 5 is defined by anaperture position in the light shielding layer. A color filter 12 isformed on a passivation film 13.

Thus the present embodiment has advantages similar to those of the firstembodiment.

However, the configuration shown in FIG. 2 may have a followingdrawback.

A chip end portion, generally involving changes in a pattern density orin a layer configuration as shown in FIG. 3, tends to result in afluctuation in the thickness of the interlayer film and the passivationfilm. As a result, a ripple in the spectral characteristics, resultingfrom multiple reflections caused by a difference in the refractiveindexes between the interlayer film and the passivation film, becomesdifferent by the difference in the thickness of the passivation film.Therefore, the spectral characteristics of the light detecting elementmay be different between an end portion and a central portion of a chip.In case a row with the light detecting aperture of the smallest area ispositioned in a chip end portion as shown in FIGS. 2 and 3, a partshowing a film thickness fluctuation represents a larger ratio withrespect to a part with a constant film thickness and may exert asignificant influence, thereby deteriorating the image quality. Also achip end portion tends to receive a stray light from an end face. InFIG. 4, “Light” indicates a stray light from the end face. Such straylight from the end face, not filtered by the color filter, may cause acolor mixing. Thus, the arrangement of the row of the smallest area ofthe light detecting aperture at the chip end portion may include a colormixing and may deteriorate the image quality.

FIG. 4 is a schematic plan view showing another configuration of thesecond embodiment of the present invention, and is a magnified viewshowing a boundary area of two adjacent semiconductor image sensors. Thestructure of a multi-chip module type semiconductor image sensor willnot be explained further, as it is already explained with reference toFIGS. 14 to 16.

FIG. 4 shows, as in FIG. 2, a case where the areas of the lightdetecting apertures are made all different among the three lightdetecting element rows, but it is different from the configuration shownin FIG. 2 in that the row having the light detecting aperture of thesmallest area is positioned in the vicinity of the peripheral circuitblock.

The embodiment shown in FIG. 4, in addition to the effects of the firstembodiment, can solve or alleviate the drawback of the configurationshown in FIG. 2 while maintaining a constant row pitch Q, therebyproviding a satisfactory image quality with a reduced color mixing.

The cross-sectional structure shown in FIG. 3 is basically same also inother embodiments. Also FIG. 3 shows a case where the aperture of thelight detecting element is defined by the light shielding film 10, butsuch structure is not restrictive. For example it may be defined by anarea of a photodiode (the fact that the aperture of the light detectingelement may be defined by the area of the photodiode being same indifferent embodiments).

Third Embodiment

FIG. 5 is a schematic plan view showing a configuration of a thirdembodiment of the present invention, and is a magnified view showing aboundary portion of two adjacent semiconductor image sensors. Thestructure of a multi-chip module type semiconductor image sensor willnot be explained further, as it is already explained with reference toFIGS. 14 to 16. The present embodiment shows a case with four rows oflight detecting elements having light detecting apertures. Recently, forimproving the color reproducibility, there is proposed a configurationhaving, in addition to the prior red, green and blue light detectingparts, a light detecting part of intermediate spectral characteristicsbetween green and blue. Also there is known another configurationhaving, in addition to the red, green and blue light detecting parts, alight detecting part for detecting an infrared light and executing animage correction by distinguishing an object of image capture and a duston the object, utilizing whether the infrared light is transmitted ornot. The third embodiment of the present invention is applicable to suchcases, and provides effects similar to those of the first and secondembodiments.

The present embodiment explains a case where a light detecting elementrow has a larger light detecting area and remaining light detectingelement rows have a same light detecting area. Now, let us consider acase where, in the four light detecting element rows, the lightdetecting areas S1, S2, S3 and S4 of the light detecting elements have arelationship S1≧S2>S3≧S4. In such case, it is desirable to position thelight detecting element rows with the light detecting elements of theareas S3 and S4 in both end rows, and not to position the lightdetecting element row with the light detecting element of the area S2,like the light detecting element row with the light detecting element ofthe area S1, in the end rows.

Fourth Embodiment

A fourth embodiment shows a case of utilizing three-color LEDs of red,green and blue as shown in FIG. 6, which shows the spectralcharacteristics thereof, with a wavelength in the abscissa and arelative light emission intensity on the ordinate. FIG. 7 shows spectralcharacteristics of the light detecting element, including the spectralcharacteristics of color filters, similarly with a wavelength in theabscissa and a relative sensitivity on the ordinate. Also FIG. 8 showsoutputs of a semiconductor image sensor utilizing LEDs shown in FIG. 6as the light source and utilizing light detecting elements of thespectral characteristics shown in FIG. 7 for image capture.

A wavelength selectivity is improved by employing LEDs of narrow lightemission wavelength ranges as the light source, in addition to the colorfilters.

As already explained, an output level of the semiconductor image sensoris determined according to the light emission characteristics of LED,the spectral characteristics of the color filter and the spectralcharacteristics of the light detecting element. Therefore, in case theused LEDs have light emission intensities of blue>green>red as shown inFIG. 6, the areas of the light detecting apertures are so designed as tohave sensitivity characteristics of blue<green<red as shown in FIG. 7,and a row with a largest aperture area is positioned in the central rowthereby providing outputs well balanced among the colors of red, greenand blue as shown in FIG. 8, while maintaining a constant row gap Q.

Fifth Embodiment

FIG. 9 is a plan view of a fifth embodiment of the present invention.The structure of a multi-chip module type semiconductor image sensorwill not be explained further, as it is already explained with referenceto FIGS. 14 to 16. In FIG. 9, 14 indicates a drive circuit for fetchinga photocharge generated in a light detecting element such as aphotodiode. The drive circuit 14 is provided for example with a CCD(charge-coupled device) register and a CMOS source-follower amplifier,and serves to transfer a weak photocharge, generated in the lightdetecting element, to an output terminal and to amplify the charge.

Japanese Patent Application Laid-open No. H11-112006 discloses aconfiguration in which the drive circuit is constituted of acharge-voltage converting means (source-follower amplifier). Nowfollowing parameters are defined as shown in FIG. 9:

-   -   L: pitch of light detecting apertures in the main scanning        direction (pitch of light detecting elements along the direction        of array in a same light detecting element row);    -   nL: pitch of light detecting apertures in the sub scanning        direction (pitch of the light detecting element rows in the        direction of arrangement thereof) (n being a positive integer,        1, 2, 3, . . . );    -   k: width of the drive circuit portion in the direction of        arrangement of the light detecting element rows;    -   a: width of a light detecting aperture of a largest area, in the        direction of arrangement of the light detecting element rows;    -   b: width of a light detecting aperture of a second largest area,        in the direction of arrangement of the light detecting element        rows; and    -   r (=a/b): an area ratio providing an optimum sensitivity        balance.

The width a of the light detecting aperture with the largest area canassume a largest value when the following relationship is satisfied.Therefore the width a is preferably so selected as to satisfy orsubstantially satisfy the following relationship. In consideration of apossible fluctuation in the manufacture, the width a may be selectedsmaller than the value given by the relationship:

${\frac{a}{2} + k + \;\frac{b}{2}} = {nL}$

This relationship can be rewritten as follows:

$a = {\frac{2r}{1 + r}\left( {{nL} - k} \right)}$

For example, for N=2, k=0 and r=2, there is obtained:

$a = {\frac{8}{3}L}$

By setting the width of the light detecting aperture so as to meet theabove-described relationship, a highest sensitivity can be realizedwhile maintaining an optimum sensitivity ratio of the rows.

The present embodiment has been explained principally in a case wherethe color filters of red, green and blue are arranged in three rows, butsuch configuration is not restrictive. Also similar effects can benaturally obtained, with color filters of complementary colors, by thearrangement of the present invention.

Sixth Embodiment

Now reference is made to FIGS. 12 and 13 for explaining an embodiment inwhich the multi-chip module type image sensor of the present inventionis applied to an original image reading apparatus of sheet feeding type.

FIG. 12 is a schematic view of an original image reading apparatus forreading an original image.

A contact image sensor 201 (hereinafter also represented as CIS) isconstituted of a multi-chip module type image sensor (photoelectricconverting device) 202, a Celfoc lens 203, an LED array 204 and acontact glass 205.

Conveying rollers 206 are positioned in front of and behind the CIS 201,and are used for positioning an original. A contact sheet 207 is usedfor contacting the original with the CIS 1. A control circuit 210processes signals from the CIS 201.

An original detecting lever 208 detects that an original is inserted.When an original is inserted, the original detecting lever 208 isinclined, thereby causing a change in the output thereof, and such stateis transmitted to a CPU 315 (FIG. 13) in the control circuit 210 wherebyan original insertion is identified. In response a driving motor (notshown) for the conveying rollers 206 is activated to start a conveyingof the original and to execute a reading operation.

FIG. 13 is a block diagram showing a detailed electrical structure ofthe control circuit 210 shown in FIG. 12. Functions of the circuit willbe explained in the following, with reference to FIG. 13.

In FIG. 13, a contact image sensor 301 (corresponding to CIS 201 in FIG.12) is integrated with an LED 302 employed as the light source. A colorimage can be read by turning on an LED control (drive) circuit 303 whilethe original is conveyed on the contact glass 205 of the CIS 201 shownin FIG. 12.

An amplifier 304 amplifies the signal from the CIS 301, and an A/Dconverter 305 executes an A/D conversion on the amplified output toprovide a digital output for example of 8 bits. A shading RAM 306 storesshading correction data by reading a calibration sheet in advance. Ashading correction circuit 307 executes a shading correction on the readimage signal, based on the data in the shading RAM 306. A peak detectioncircuit 308 detects a peak value in the read image data in each line,and is used for detecting a leading end of the original.

A gamma conversion circuit 309 executes a gamma conversion on the readimage data, according to a gamma curve set in advance by a hostcomputer.

A buffer RAM 310 is a random access memory for temporarily storing imagedata, in order to match the timing of the actual image reading operationwith a communication with the host computer. A packing/buffer RAMcontrol circuit 311 executes a data packing process according to animage output mode (such as binary, 4-bit multi-value, 8-bit multi-valueor 24-bit multi-value) set in advance by the host computer. It alsoexecutes a process of writing such data thereafter in the buffer RAM310, and a data output process of reading the image data from the bufferRAM 310 into an interface circuit 312.

An interface circuit 312 executes a control signal exchange with and animage signal output to an external apparatus, for example a personalcomputer, serving as a host apparatus of the image reading apparatus ofthe present embodiment.

A CPU 315, constituted for example of a microcomputer, is provided witha ROM 315A storing process programs and a working RAM 315B, and controlsvarious parts according to the programs stored in the ROM 315A.

There are also provided a crystal oscillator 316, a timing signalgenerator 314 for generating various timing signals, to be used asreferences for operations, by a frequency division on the output of theoscillator 316 according to a setting by the CPU 315, and an externalapparatus 313 such as a personal computer, connected with the controlcircuit through the interface circuit 312.

The present invention is applicable to an image sensor, or a multi-chipmodule type image sensor, a contact image sensor or an image readingapparatus formed by arranging plural image sensors in an array.

This application claims priority from Japanese Patent Application No.2005-056018 filed Mar. 1, 2005, which is hereby incorporated byreference herein.

1. An image sensor comprising at least three light detecting elementrows each having plural light detecting elements and a color filterprovided on each light detecting element, in which the light detectingelement in one of the light detecting element row has a light detectingarea larger than that of the light detecting element in the others ofthe light detecting element rows, and the light detecting element rowsare arranged so that centers of gravity of light detecting parts of thelight detecting elements in the respective light detecting element rowsare arranged at a constant pitch: wherein the light detecting elementrow with a larger light detecting area of the light detecting element ispositioned between said other light detecting element rows of thesmaller light detecting area of the light detecting element.
 2. An imagesensor comprising at least three light detecting element rows eachhaving plural light detecting elements and a color filter provided oneach light detecting element, in which the light detecting element in atleast one light detecting element row has a light detecting area largerthan that in the light detecting element in others at least two lightdetecting element rows, and the light detecting element rows arearranged such that centers of gravity of light detecting parts of thelight detecting elements in the respective light detecting element rowsare arranged at a constant pitch: wherein the at least one lightdetecting element row with a larger light detecting area of the lightdetecting element is positioned between said other light detectingelement rows with a smaller light detecting area of the light detectingelements.
 3. An image sensor according to claim 2, where a pitch of theat least three light detecting element rows along a direction ofarrangement thereof is equal to or an integral multiple of a pitch ofthe light detecting elements along a direction of array thereof in theat least three light detecting element rows.
 4. A multi-chip module typeimage sensor comprising a plurality of image sensors according to claim2, positioned in such an array that end portions thereof are mutuallyadjacent.
 5. A contact image sensor comprising a multi-chip module typeimage sensor according to claim 4, a light source for irradiating anobject of image reading with a light, and an optical system for guidinga light from the object of image reading to the multi-chip module typeimage sensor.
 6. A contact image sensor according to claim 5, whereinthe light source is an LED having light emission characteristicscorresponding to spectral characteristics of the color filter.
 7. Animage reading apparatus comprising a contact image sensor according toclaim 5, and a roller for conveying an original, constituting the objectof image reading, to the contact image sensor.